That episode signaled how abruptly the politics of U.S. warmaking have changed, as the intervention in Libya follows a bloody, weary decade in Afghanistan and Iraq.

Now, a Democratic president has asked the country to support a new military action and missed a legal deadline that required him to get Congress’s authorization.

In response, an antiwar movement has appeared in an unlikely place: a House dominated by the Republican right.

“We are in control in the House, and we want something on the floor,” said Rep. John Campbell (R-Calif.), one of a number of conservatives who called Wednesday for a showdown with Obama. “Put a resolution up, and let us express . . . to the president that ‘you no longer have the authority of this Congress to conduct military operations in that country.’ ”

Since the beginning of the Libyan operation, congressional leaders have been quietly supportive of Obama — but mostly just quiet. In the Senate, a resolution in support of the president is still waiting for a vote.

In the House, GOP leaders had said little on the subject, even after Obama missed a deadline set in the 1973 War Powers Resolution. That law required him to obtain congressional permission within 60 days, a deadline that passed last month.

“His intention is not to undermine the commander in chief, at a time when we have troops in harm’s way,” Kevin Smith, a spokesman for House Speaker John A. Boehner (R-Ohio), said Wednesday.

But also on Wednesday, discontent with that military operation — and with warmaking in general — seemed to boil over.

An early warning had come the week before, when the House narrowly voted down a proposal to demand a speedy transition of U.S. forces out of Afghanistan. In 2010, a similar bill garnered 162 votes in defeat, including nine Republican votes. This time, it still lost — but with 204 votes, including 26 Republican votes.

On Wednesday, the bill at issue was far more drastic. Introduced by Rep. Dennis J. Kucinich (D-Ohio), it would demand that Obama withdraw forces from the Libyan operation within 15 days. That would be a crippling loss for the NATO-led campaign, which relies heavily on U.S. air power.

The resolution looked, a week before, like a legislative long shot.

Then, on Wednesday, it wasn’t.

“There’s been disquiet for a long time,” said Rep. Jeff Flake (R-Ariz.), one of those who supported it. “Republicans have been too eager to support some military ventures abroad. And this, I think, is perhaps a little more consistent with traditional conservatism.”

Conservatives expressed support for the bill in a closed meeting, but GOP leaders put off the vote. Instead, they said they would gather all 200-plus House Republicans to discuss Libya again Thursday afternoon.

Rep. Dan Burton (R-Ind.), who co-sponsored Kucinich’s bill, said he would press for GOP leadership to bring it up for a vote.

“I think, in the House, there’s probably enough votes to pass this,” Burton said. Also Wednesday, Rep. Thomas J. Rooney (R-Fla.) introduced a similar bill, which would require Obama to obtain Congress’ approval by June 19 or begin withdrawing troops.

House Democrats would likely be split on the issue. Several liberals have followed Kucinich, blasting Obama for missing the 60-day deadline. But Rep. Steny H. Hoyer (D-Md.), the second-ranking Democrat, said earlier this week that he would not support Kucinich’s bill.

“To the extent that it calls for . . . withdrawal, that means not supporting the NATO allies who jointly undertook this enterprise, I think that would mean I’m not going to support that,” Hoyer said in a press briefing.

At the White House on Wednesday, press secretary Jay Carney said only that Obama would wait to see what Congress does.

“We feel strongly that the president has acted in a way that is consistent with the War Powers Resolution,” Carney said.

If the House does seek a showdown with Obama over Libya, it would be bucking a Capitol Hill tradition that goes back generations. Most legislators, no matter what their party, have been reluctant to meddle in military campaigns that presidents have already begun.

On Wednesday, some legislators said they were worried whether Congress had the stomach to see that sort of confrontation through.

“We’ve got to be honest with ourselves: The answer is no, I don’t think so. Why not? Because it’s easier to let somebody else carry that load [of guiding a war effort], and then applaud or blame,” said Rep. John Garamendi (D-Calif.), who said Obama has not clearly articulated the U.S. strategy in Libya.